Wendiceratops: a richly sampled but disarticulated horned dinosaur

Wendiceratops pinhornensis was a centrosaurine horned dinosaur from the Campanian Oldman Formation of Alberta, Canada. Its fossils are striking for two different reasons: the frill carries large ornaments that curve forward, and the bonebed contains more than two hundred remains from several individuals. The sample is rich but disarticulated, so it reveals many anatomical details without preserving a complete skeleton or a single moment of group behaviour.

Quick facts

Wendy Sloboda and the Pinhorn bonebed

Fossil hunter Wendy Sloboda discovered the locality in 2010 in the Pinhorn grazing reserve. Excavations from 2011 to 2014 exposed a dense layer of bones in a carbonaceous sandy mudstone in the lower Oldman Formation. David Evans and Michael Ryan named the species in 2015. The genus name honours Sloboda; the species name refers to Pinhorn.

The holotype, TMP 2011.051.0009, is a partial right parietal, one of the bones that formed the frill. Other bones from the site were assigned to Wendiceratops because the diagnostic ceratopsid material matched the holotype and came from the same concentrated deposit. The sample includes remains from multiple sizes and represents most regions of the skeleton, but the bones were not found in anatomical order.

What the frill ornaments preserve

The rear of the skull formed a broad parietal frill with large marginal ornaments. In Wendiceratops, several of these projections curve forward over the frill. Their bases and shapes are directly preserved in the parietal bones, making the species useful for comparing the rapid variety of centrosaurine headgear.

Part of the nasal bone preserves the base of a prominent nasal horn. The complete horn is missing, so its full height, curvature and exact profile must be reconstructed. Illustrations often show a tall upright horn, but the fossil evidence is strongest at its base. Horn shape should not be described as fully known.

These ornaments help researchers compare ceratopsids, but they do not by themselves demonstrate a specific behaviour. Display, species recognition and competition are possible functions of head ornamentation. The bones do not record a courtship display, a fight or the animal’s colour.

Age and the lower Oldman Formation

The bonebed lies in the lower part of the Oldman Formation, around ten metres above its contact with the Foremost Formation. Correlation with dated rocks in the Judith River Group places it at roughly 79.0–78.7 million years ago, in the middle Campanian. This is a geological age range, not a precise date assigned to each bone.

Fine-grained river-plain deposits, root traces and organic-rich layers indicate lowland settings with channels, floodplains and waterlogged ground. The bones are disarticulated but show limited weathering and abrasion. Some joints at the ends of long bones are missing, consistent with loss of cartilage-rich areas before or during burial. The accumulation was close to where the animals died or were deposited, but water and decay altered the assemblage.

What a bonebed does not prove

The concentration includes multiple individuals and may reflect a population-level event or a series of remains gathered in the same depositional setting. It does not preserve a group of complete skeletons positioned together. Without articulation and fine-scale taphonomic evidence, the site cannot establish that the dinosaurs travelled as a herd, died simultaneously or were killed by one event.

Bonebeds can form through several processes: repeated mortality at a locality, floods that concentrate remains, or the gradual accumulation and reworking of carcasses. Researchers consider articulation, abrasion, weathering, bone orientation and sedimentary context together. Wendiceratops provides a strong anatomical sample, but behavioural claims must remain more cautious than descriptions of the frill bones.

Classification among centrosaurines

Wendiceratops belongs to Ceratopsidae and is usually placed in Centrosaurinae. Its horn and frill characters help diagnose the species, but different phylogenetic analyses can recover different relationships among closely related centrosaurines. A distinctive ornament does not make an animal the direct ancestor of another horned dinosaur.

The lower Oldman assemblage also sits within a changing Campanian fauna. Fossils from formations across Alberta and Montana document related but not identical communities through time. For comparisons with other horned dinosaurs, see the A–Z dinosaur catalogue; the catalogue’s sequence is for navigation, not a family tree.

What remains unknown

Wendiceratops is better represented than many centrosaurines, but its complete skull and body proportions still have to be assembled from separate bones. The nasal horn’s full shape, the cause of the bonebed and the social behaviour of the animals are not directly preserved. What is clear is the distinctive frill, the presence of multiple individuals and the geological setting that brought their remains together.